I don't think a membership fee is a good way to solve the problem, because I don't think the problem has anything to do with fees. I think the problem is that our community is too popular, and the curious outsiders are starting to outnumber the insiders. Since the outsiders are more likely to have day jobs than the insiders, having a fee would probably increase the ratio of outsiders to insiders.

I think proggit is doing more to keep the HN community focused than charging a fee would, as it scoops up some of the people who are bored at their day jobs and curious enough to read about hacking but not to actually hack. :)